This invention relates generally to sawmill guide rails, and more particularly to a unique new sawmill guide rail which provides a quick, simple and accurate method of aligning the guide rail to the sawmill saw blade.
Sawmills, as utilized in commercial operations, typically comprise three individual main parts; namely (1) the frame, or husk, which contains the saw blade and the saw blade drive machinery, (2) the carriage upon which the logs are mounted and which carries the log into the saw blade so that lumber can be cut from the log, and (3) a pair of tracks upon which the carriage rolls Such sawmills may utilize either a circular saw blade, or a band saw blade. Band saw blades may be either single cut, having teeth only on one edge thereof, or double cut, having teeth on both edges thereof. The double cut band saw blades offers the advantage of increased production in that the log can be cut as the carriage is moved in either directions.
The carriage is normally a large rectangular frame member mounted on two or more axles with steel wheels thereon which are adapted to roll on the pair of tracks. The upper surface of the carriage is provided with two or more clamping devices adapted to securely grip a log and hold it in a longitudinal fixed position on the carriage, with one side of the log extending beyond the edge of the carriage. Accordingly, movement of the carriage along the tracks in front of the saw blade will advance the log into the saw blade so that a length of board is cut therefrom.
As should be apparent, the tracks are parallel to each other, and must also be parallel to the saw line, i.e. parallel to the plane of motion of the saw blade, passing in front thereof, so that the carriage will move over the tracks passing in front of the saw blade in a path parallel to the saw line.
Normally, the two parallel tracks are not identical, in that one is merely a flat length of steel for support of the carriage and the load thereon. The other track, however, is a guide rail which serves the same function in supporting the carriage and its load, but in addition serves to guide the carriage movement with reference to the saw blade, in a very straight and horizontal path parallel to the saw line. The guide rail is normally a true rail having a flange at the bottom, a head at the top and a web therebetween. Unlike conventional railroad or trolly rails, however, the saw mill guide rail head must have one or more accurately formed surfaces which serve to control the rolling movement of a guide wheel thereon in a very true straight path. Normally, the guide rail head is provided with two beveled surfaces, with one such surface on each side of the rail head adapted to support and guide mating flanges on either side of the carriage guide wheels riding thereon. The beveled head surfaces are carefully machined to provide exacting dimensions and angles, with the resulting head having a frusto-conical cross-section. Such guide rails are often times referred to as a V-track. The purpose of the beveled surfaces is to keep the carriage guide wheels securely aligned on the rail without any possibility of axial motion of the wheel on the rail. To this end, the carriage guide wheels riding on the guide rail are dimensioned such that two opposed flanges thereon are the only portion of the guide wheels in contact with the rail, so that the flanges on the carriage guide wheels will ride on and follow the true straight beveled surfaces of the guide rail. The spacing between the two wheel flanges is intentionally maintained to be sufficiently narrower than the upper horizontal surface of the rail head so that the cylindrical face of the guide wheel between the flanges, does not itself engage or contact any portion of the guide rail. Therefore, the carriage travel is more accurately controlled since the path of travel is controlled only by the flanges of the guide wheels riding on the beveled guide surfaces of the rail head.
Since only one guide rail is essential to keep the carriage motion in a straight line, the other rail is normally just a flat steel track upon which flat cylindrical carriage wheels ride. Normally the guide rail is located as the track furthest from the saw blade to minimize the chances of saw dust and bark falling thereon and causing a distortion in the path of travel or even carriage derailment.
It is of critical importance that the sawmill tracks, particularly the guide rail, be very accurately aligned so that the carriage will travel in a single, horizontal plane, and in a very straight line, as perfectly parallel as possible to the saw blade and saw line. In order to maintain proper alignment of all components, is it of course essential that the frame and rails be mounted on firm, solid footings and supports so that the components will retain a proper alignment during use.
Since the guide wheels on one side of the carriage are different from the flat wheels on the other side of the carriage, the radius of the two different types of wheels may not be identical from the axis to the point of contact with the track. Therefore, the two tracks may not necessarily lie in the same plane, but they should, nevertheless, lie in planes that are parallel, so that the carriage will travel thereon in a flat horizontal path throughout its length of travel.
The typical procedure for aligning the tracks usually involves the temporary fastening of the tracks in place, beginning next to the saw blade, assuring that they are properly spaced therefrom and parallel thereto, and then working outward in both directions to align each successive length of track. The tracks are generally leveled in a horizontal plane using a level and wedges or shims where necessary. After the tracks are temporarily secured in place and properly spaced from the saw blade, the guide rail must be aligned in a straight line, spaced from and parallel to the saw blade cutting line. To do this, a length of string, or preferably piano wire, is stretched alternately along the upper surface of the rail head and along the side surface of the rail head while the rail's position is adjusted to be properly aligned for straightness and flatness with the stretched string or piano wire. This later procedure is not only time consuming and labor intensive, but is not as accurate as could be desired. Indeed, the stretched string or piano wire will always have some degree of sag, and the string or piano wire cannot be permitted to contact the rail least such contact will cause some deviation from a true straight line. Since the string or piano wire cannot contact the rail head, such an alignment procedure is at best an eye-ball determination of alignment, subject to human judgment, and of course, human error.